Magnetoresistive sensors, such as giant magneto resistance (GMR) sensors, can be used in various angular position sensing applications, including steering angle sensing in automotive applications and in brushless DC motor commutation and rotary switch applications. In use, the resistance of GMR layers in a GMR angle sensor varies in response to an angle between the magnetization of a free layer and a reference direction. The reference direction can be defined by a hard, or permanent, magnetic magnetization of a reference layer of the angle sensor. The resistance of a GMR resistor can be expressed as:R=R0*(1+GMR*cos(phi))where phi is the angle between the magnetization of the reference layer and the magnetization of the free layer, R0 is the resistance at phi=90 degrees, and GMR is a dimensionless number specifying the strength of the GMR effect.
Anisotropic magneto resistance (AMR) sensors are also known and have a resistance that is a function of an angle between an applied magnetic field and current flow lines through a soft magnetic electrically conducting layer:R=R0*(1+AMR*(cos(psi))2)where psi is the angle between the current flowlines and the magnetization of the soft magnetic layer, R0 is the resistance at psi=90 degrees, and AMR is a dimensionless number specifying the strength of the AMR effect.
Both GMR and AMR resistors can generally comprise metallic thin films having small sheet resistances such that many strips arranged in serpentines are used to build up larger resistors. A drawback of GMR resistors, however, is that they also have small AMR effects, which can distort results. The resistance of a GMR resistor when considering the AMR effect can be expressed as:R=R0*(1+GMR*cos(phi)+AMR*(cos(psi))2)
Therefore, there is a need for a GMR angle sensor having a reduced AMR effect.